Over the years, that I've had Olympus equip. I've often thought about getting one of these, largely as a low light solution. Unfortunately each time I started looking, I read too many differing opinions about the quality of the lenses as well as Sigma's inconsistent quality control relative to these two lenses.
Ultimately, I went in a different direction and wound up buying a Minolta Rokkor 50mm f1.4 lens and an adapter from Fotodiox. The combination cost me a total of $75 USD.

Granted, this a is a manual focus solution. But, for my purposes- taking photos of static subjects, it worked quite well.